On‐Line Monitoring of Flavour Processes

Abstract

The aim of this chapter is to introduce readers to the techniques used to monitor flavours on-line. The rationale for on-line monitoring is given, along with the analytical requirements for the real time, in vivo measurement of aroma release. This sets the specification for the analytical method as well as demonstrating some of the difficulties and limitations associated with on-line flavour analysis. A brief history of on-line analysis is given to explain how the current techniques evolved and this is followed by an overview of the techniques currently available. Finally, examples of applying on-line monitoring of flavours are given to illustrate the power of the technique, and some future needs and trends are discussed. INTRODUCTIONAnalysis of flavour compounds has been a major interest for analysts and for flavour technologists over many years. On the analytical side, the advent of gas chromatography (GC) and then high-performance liquid chromatography (HPLC) allowed the detailed composition of many flavour materials to be elucidated in terms of compound identification and quantification. Besides giving food technologists a powerful tool to study the composition of flavours, the data could also be used to link flavour composition with sensory flavour quality. In other words, the aim was to understand questions such as the following: r Why do particular mixtures of compounds taste pleasant? r Why do quite small changes in some flavour components cause significant changes in sensory scores?Although understanding the link between composition and sensory quality is an attractive idea, there are very few published papers that compare the flavour composition of a product to its sensory attributes. One example is that of Togari et al. (1995) who used a chemometric approach to correlate flavour compositions of different tea samples with individual sensory attributes. The various sensory attributes of tea (e.g. the 'fresh floral' attribute) were expressed as equations based on the concentrations of those compounds that contributed positively and negatively to the sensory attribute, with each compound being given a weighting, calculated to give the best fit of the experimental data Food Flavour Technology: Second Edition Edited

An atmospheric pressure chemical ionization–ion‐trap mass spectrometer for the on‐line analysis of volatile compounds in foods: a tool for linking aroma release to aroma perception

“…Thus, time‐intensity (TI) methods aim at measuring the variation of the perceived intensity of a single particular sensory attribute with time. Conducted simultaneously or in parallel with nosespace analyses, correlations between retronasal aroma release and aroma perception could be stressed . However, as a single sensory descriptor may be followed each time in an experiment, several TI experiments are required to evaluate several attributes.…”

“…Based on early work on breath analysis using APCI-MS, [7] APCI-MS systems were developed for in vivo flavour release analysis (called 'nosespace' or breath-by-breath analysis). [1] The so-called 'MS-nose' system developed by Taylor's group in Nottingham has been used in numerous studies, [8] and its sensitivity and linearity have been recently evaluated to be superior to that of an optimized PTR-MS. [9] Usually APCI instruments for flavour release applications are run with quadrupole MS analysers. To reach a sufficient time resolution and sensitivity, they need to be run in the multiple-ion detection mode that limits the practical measurable number of ions (i.e.…”

Volatile compounds profiling by using proton transfer reaction‐time of flight‐mass spectrometry (PTR‐ToF‐MS). The case study of dark chocolates organoleptic differences

“…For years, APCI-MS has been the reference technique for in vitro and in vivo monitoring of flavour compounds, [46][47][48][49] and the method with its advantages and drawbacks were reviewed in detail elsewhere. [49][50][51] Portable APCI instruments were developed, [52][53][54][55] and such a compact mass spectrometer has been recently used efficiently for discriminating between different varieties of cheese and monitoring the spoilage of meats. 56 As APCI accomplishes the whole process of reagent ions formation and proton transfer to the analytes in a small source region, it suffers from problems of suppression of ionization and relatively low ionization efficiency.…”

“…Precursor ions are formed in this small region by a corona discharge ionizing the sample air constituents to form predominantly hydronium ions that subsequently protonate neutral molecules present in the sample gas with limited fragmentations. For years, APCI‐MS has been the reference technique for in vitro and in vivo monitoring of flavour compounds, and the method with its advantages and drawbacks were reviewed in detail elsewhere . Portable APCI instruments were developed, and such a compact mass spectrometer has been recently used efficiently for discriminating between different varieties of cheese and monitoring the spoilage of meats .…”

Determination of volatile aroma compounds of <i>Ganoderma lucidum</i> by gas chromatography mass spectrometry (HS-GC/MS)

“…Among the detected alcohols 1-Octen-3-ol was detected as the major one. 1-Octen-3-ol (mushroom, butter, resinous), 3-Octanol (fruity, cod liver oil, citrus, weakly nutty, fungal), 1-Octanol (fruity-flowery, sweet soap, orange, waxy, sweet) 1-Octen-3-one (boiled mushrooms, metallic, fungal, wild mushroom), 3-Octanone (fruity, sweet, musty, floral, lavender, sweet ester), 2-Octen-3-ol and 3-Octanal are the well-known and common aroma compounds (Jong and Birmingham, 1993;Taylor and Linforth, 2010). The identified aldehydes were detected as 3-methyl butanal, 2-Octenal, pentanal, 2,4-Decadienal, 1-Proponal.…”